A terminal box that includes an output part of a solar cell module is a box for housing an electric circuit in a case having one side open. The electric circuit includes a terminal base, a terminal block, and the like. On the terminal base, an electrode of the solar cell is connected. In the terminal block, an electric wire of a bypass diode and an output cable are connected to the terminal base. A potting material is applied on and around the electric circuit, and the side left open of the case is closed with a lid (for example, refer to the patent literature 1).
The Patent Literature 1
Japanese Patent Application Laid-Open No. 2001-168368.
The terminal boxes are of a type in which the output cable is already connected at the time of shipment, and a type in which the output cable is connected at a site of installation of a solar cell module. The terminal box of the type in which the output cable is connected at the installation site does not have a cable hole, which is a through hole, at the time of shipment; therefore, the cable hole is made, before connecting the output cable, at the installation site.
The portion of the terminal box where the cable hole is to be made on a side plate of the terminal box has a thin portion inside an annular groove, and it is possible to make a through hole by knocking out and removing a disk part inside the annular groove.
However, the conventional terminal box described above has a structure that the electric circuit is exposed when the lid of the terminal box is removed. Therefore, there has been a problem that, if heat is generated at the electric circuit due to a bad connection caused by a loosened or insufficiently tightened screw that connects the electric wire of the output cable to the terminal base in the terminal block, the lid and the terminal block that are formed with a thermoplastic resin melt, and the electric circuit becomes exposed outside the terminal box, resulting in a short circuit.
Moreover, the case of the terminal box is sometimes damaged while making the cable hole, due to slipping of a rod-shaped knockout tool when hit with a hammer. This case has also been causing the problem that the electric circuit becomes exposed outside the terminal box, resulting in a short circuit.
In view of the above description, it is an object of the present invention to provide a terminal box of which a lid and a terminal block do not melt or do not take fire even when heat is generated at an electric circuit, and of which a case is not damaged while knocking out when making the cable hole.